This invention relates generally to mobile machines for mixing concrete on-site, and more particularly, to a mixing auger apparatus for use on concrete trucks.
Concrete trucks, such as that described in U.S. Pat. No. 3,310,293, issued to Harold M. Zimmerman on Mar. 21, 1967, and U.S. Pat. No. 4,406,548, issued to Paul M. Haws on Sep. 27, 1983, carry supplies, such as aggregate, cement and water, in discrete hoppers from which the supplies are drawn in predetermined ratios to be deposited in a mixing auger apparatus where the combined supplies are mixed and turned into concrete to be discharged from the mixing auger externally of the concrete truck. This mixing auger apparatus is formed from a generally semi-circular flexible housing against which a standard pitch, spiral flighted auger works to not only mix the combined supplies, but to convey the combined supplies, and ultimately the created concrete, to the remote discharge end of the auger.
This mixing auger apparatus was limited in use to a maximum vertical angle of inclination of approximately 22.degree. from horizontal. If the mixing auger were inclined at an angle greater than approximately 22.degree., the water and/or other liquid supplies would not be properly conveyed by the standard flight auger along the semi-circular housing, preventing the combined supplies from properly mixing to create concrete. Typically, the liquid supplies would "splash back" over top of the mixing auger, rather than be conveyed upwardly toward the discharge end of the auger.
It is known in the auger arts that the use of a half pitch auger, i.e. an auger whose axial spacing of flighting is generally equal to half the diameter of the auger flighting, as opposed to a standard pitch auger whose axial spacing of flighting is approximately equal to the diameter of the auger flighting, will improve the ability to convey liquid materials upwardly over vertical inclinations greater than 22.degree.. The use of a flexible housing to cooperate with the auger flighting allows the mixing auger apparatus to convey conventional sized aggregate used to create concrete without either becoming pulverized by the action of the auger or damaging the auger by becoming wedged between the flighting and the housing.
Conventional concrete mixers have utilized a drum mounted on a truck frame to deliver mixed concrete to a delivery site by discharging the mixed concrete from the elevated, rearwardly directed, central discharge opening of the drum. More recent variations of the conventional concrete mixers have reoriented the drum to position the discharge opening toward the front of the truck, which enables the operator to control the discharge and delivery of the mixed concrete through a front-mounted discharge chute mechanism without leaving the cab of the truck.
Concrete trucks, as described in the aforementioned U.S. Pat. Nos. 3,310,293 and 4,406,548, located the mixing auger apparatus at the rear of the truck to receive the respective supplies fed downwardly and rearwardly thereto. The upward incline of the mixing auger allowed the mixed concrete to be discharged from a slightly elevated position to be delivered through a cooperative discharge chute mechanism. A mere repositioning of the mixing auger apparatus to the front of the truck to enable the forward discharge of the mixed concrete forwardly thereof is not a simple design choice as the operator's cab of the truck prevents the relocation of the mixing auger apparatus to the opposing front position. The forwardly delivering concrete truck must be capable of delivering mixed concrete at a forward position above the cab of the truck so that a discharge chute mechanism, which must be storable in a transport position above the truck cab out of the line of sight of the operator, can deliver the mixed concrete to the ground forwardly of the truck.
Accordingly, it would be desirable to provide a concrete machine operable to mix supplies of materials on-site that would be capable of discharging the mixed concrete forwardly of the concrete truck. It would be further desirable to provide a mixing auger apparatus that would be operable to combine supplies of materials needed to create concrete and delivered thereto, and be able to convey the combining materials along the length of the mixing auger even though the mixing auger is inclined at an angle greater than 22.degree. to the horizontal, which would enable the discharge of mixed concrete therefrom at a position elevated above the cab of the concrete truck. It would also be desirable to provide an adjustment apparatus to compensate for wear between the mixing auger and the flexible housing so that the mixing auger apparatus can be efficiently operated at an angle greater than 22.degree. for a greater life.